1. Field
The disclosure of this application relates generally to medical devices, and in particular it relates to a needle placement manipulator with two rotary guides slanted with respect to each other, and to a needle guidance system equipped with the needle placement manipulator.
2. Related Art
The use of imaging modalities, such as ultrasound, mammography, computed tomography (CT), Magnetic Resonance Imaging (MRI) and the like, to assist in identifying and treating abnormalities within the body of a patient, has gained increased acceptance in the medical field. The above-named and other imaging modalities generally provide good contrast between different soft tissues of the body. Thus, many of these techniques are being used to depict the boundaries of damaged tissue within healthy tissue for accurate identification and treatment. Advanced diagnostic procedures, however, require further validation and refinement in localization of damaged tissue. This further validation and advanced localization can be performed by needle biopsy procedures. To help define the boundaries of damaged tissue within healthy tissue with greater accuracy, needle guidance systems have been proposed.
A non-patent literature article entitled “MRI Guided Needle Insertion—Comparison of Four Techniques”, by Fisher et al., describes four techniques for needle placement: 1) image overlay that projects an MR image and virtual needle guide on the patient, 2) biplane laser with needle trajectory marked by intersecting transverse and oblique sagittal lasers, 3) handheld protractor with pre-angled guide sleeve, and 4) freehand insertion. Conventionally, all of these techniques have required removing the patient out the imaging modality for needle insertion.
In the medical environment, it is necessary to position a needle tip precisely inside tissue or a specific organ for accurate diagnosis or minimal invasive therapy. Biopsy, ablation, cryotherapy, aspiration and drug delivery are examples that require high precision needle placement. Prior to a percutaneous incision, a target area of interest (e.g., tumor, nodule, etc.) is confirmed by means of non-invasive imaging with MRI, ultrasound or other imaging modality. Once the target area of interest is positively determined, the clinician decides an entry point, inserting direction and depth to be reached by the needle based on experience. This process often requires a lengthy trial and error routine, which can be deleterious to the patient. Accordingly, in the last few decades there has been an increased interest in the development of needle guiding systems that can improve accuracy of needle positioning, minimize patient discomfort, and shorten time of operation.
In the realm of needle guiding systems having a handheld protractor with pre-angled guide sleeve, US Patent Application Publication 2011/0190787 disclosed by Hirdesh Sahni (herein “Sahni”) is an example. Sahni describes an “IMAGE GUIDED WHOLE BODY STEREOTACTIC NEEDLE PLACEMENT DEVICE with FALLING ARC”. In Sahni's system, the device may be compatible with both CT and MRI modalities, but the patient has to hold the breath while the needle is being passed into regions that move on respiration. The device can be placed on the skin or on near an exposed organ of a patient, but its function can be jeopardized by movement.
In the realm of modality-guided needle placement systems, US Patent Application Publication 2006/0229641 disclosed by Rajiv Gupta et al., (herein “Gupta”) is an example. Gupta describes a “GUIDANCE AND INSERTION SYSTEM”, in which the insertion angle of the needle is guided by two arc-shaped arms which are driven by motors respectively attached at the axis of each arm. The device can be configured for use with an imaging apparatus, such as CT scanner, to allow the device and tool to be operated while viewing the device positioned in relation to a target surgical site. The device can be placed on a patient's skin and fastened by belts. The device can passively compensate for patient's movement.
In MRI-guided percutaneous interventions, accurate needle placement is of great concern and of considerably more difficulty that in needle placement systems for other modalities, such as CT or ultrasound. Unlike other modalities, MRI makes use of the property of nuclear magnetic resonance (NMR) to image nuclei of atoms inside the body. To that end, during an MRI scan, a patient is disposed within a powerful magnet where a large magnetic field is used to align the magnetization of atomic nuclei in the patient's body, and a radio frequency (RF) pulse is applied to alter the linear magnetization of the atomic nuclei. This causes the atomic nuclei to absorb energy from tuned radiofrequency pulses, and emit radiofrequency signals as their excitation decays. These signals, which vary in intensity according to nuclear abundance and molecular chemical environment, are converted into sets of tomographic (selected planes) images by using field gradients in the magnetic field, which in turn permits 3-dimensional (3D) localization of the point sources of the signals (or damaged tissue). More specifically, the detected signals are used to construct 2D or 3D MRI images of the scanned area of the body.
In an MRI-guided needle placement system, therefore, it is preferred that the entire positioning system consists essentially of non-magnetic materials such that there is no danger of impairing the homogeneity of the magnetic field within an examination volume. In addition, in order to track spatial positioning of the needle with respect to the guiding system, it is necessary to provide a marking point, such as a MR measurable fiduciary mechanically rigidly connected to the guiding system. In this manner, the position of the manipulator itself can be determined via MR measurement. U.S. Pat. No.: 6,185,445 to Knuttel discloses and example of such system.
Shortcomings of conventional technology include: 1. Rigidity of the guide is required to insert a needle with accurate position and posture. But rigidity of arc-shaped arm is low, and in particular rigidity of arc-shaped guides including attached motor is also low. 2. Arc-shaped arms provide visibility, so that a clinician can see the needle entry point, but opening is too small to access the entry point.